/Engine/Source/Developer/Datasmith/DatasmithExporter/Public/DatasmithExportOptions.h
Never: it won't force the creation of a UV channel for lightmap, if one already exists it will be exported IfNotPresent: if a channel already exists it will be used, if not a new automatic UV projection will be created Always: it will create the UV channel overwritting existing data
enum EDSExportLightmapUV { Never, IfNotPresent, Always, }